For many, many months, I have had a rattling sound coming from my handlebar / stem area while riding, or when bouncing the front of my bike on the ground while stationary. At first, I figured it was a cable banging against something metallic, but after much investigation, I could not find the source. I came to the conclusion that the only thing it could be was a loose stem.
So, after many months, I decided to tighten it up to see if that made a difference. 5 minutes later, and it’s fixed. Why did I leave it that long?
The main thing to know when trying this for yourself is the order that you need to loosen and tighten the bolts. In the picture, you can see one bolt on the top of the stem, and there are two down the side; you can only see one on the side, because the other bolt is facing the other direction, which is fairly normal for a stem.
When you are tightening a stem up, you first tighten the top bolt, and then tighten the side bolts. This ensures that the top cap is compressed as much as it should be before you then tighten the side bolts – doing it the other way would prevent the top cap pushing down, which is what it is meant to be doing. When loosening, you do the reverse. Simples!